The field of the invention is that of the functionalization of linear or cyclic silicones, in particular polyorganosiloxanes, consisting of M, D, T and optionally Q units.
The POSs to be functionalized, which are more specifically addressed in the context of the invention, are linear or cyclic polyorganohydrosiloxanes. It is the SiH groups of these POSs which serve as attachment points, to functionalities intended to substitute these POSs, in order to give them specific properties, for example anti-adhesion, lubrication, compatibilization, etc., which are all properties that are desired in the diverse and varied applications of silicones.
The present invention relates to the industrial-scale manufacture of multifunctional POSs. In such a context, it is clear that continuous or semi- continuous operating modes are more suited to the industrial requirements of viability and productivity than in the batchwise mode.
The present invention is also directed towards an industrial unit for the manufacture of multifunctional PoSs, in particular according to the process outlined above.
The actual principle of the multi-functionalization of POSs is described in the prior international patent application PCT WO 96/16125. That document discloses the preparation of a POS II containing Sixe2x80x94OEt and Sixe2x80x94H functionality, by dehydrocondensation of polymethylhydrosiloxane xcex1-xcfx89-Si(Me)3 containing, for example, 50 MeSiHO2/2 units. In place of the ethoxy functionality, other alkoxyls are envisaged, such as, e.g. isopropoxy.
The dehydrocondensation is carried out by placing the POS (I) containing SiH in contact with an alcohol which is a precursor of the alkoxy functionality, in the presence of a platinum-based catalyst.
After this dehydrocondensation, a fraction of the starting SiH groups is found to be substituted with an alkoxy residue.
The POS (II) thus obtained is then subjected to hydrosilylation of an olefin, such as octene, by the remaining SiH groups and in the presence of the starting platinum catalyst.
It could thus be observed that the dehydrocondensation of POS (I) containing SiH, with excess alcohol and in the presence of a platinum catalyst, slows down considerably to about a 66% degree of conversion.
Faced with the problem of industrialization of this process for the multi-functionalization of POSs containing SiH groups, the Applicant has had to confront a certain number of technological and technical difficulties, which will be outlined below.
The general specifications sheet for an industrial process for the manufacture of multi-functionalized POSs comprises at least four main requirements: productivity and viability, the quality of the finished products, safety, and the ease of implementation.
As regards the productivity and viability, it is clear, as already indicated above, that a continuous, or even semi-continuous, operating mode must be envisaged.
One of the deciding factors of the quality of the multifunctionalized POSs considered is based on controlling the degree of conversion of the SiH groups by dehydrocondensation (degree of substitution by a first type of functionality). In the case where the alcohol is used as dehydrocondensation reactant, it is important to control the degree of partial alkoxylation in order to ensure its reproducibility. The only close prior art in this respect, namely application PCT WO 96/16125, provides no solution (nor even the start of a solution) since the examples it gives are laboratory tests performed, in a batchwise manner, in 500 ml three-necked round-bottomed flasks.
The industrial safety aspect is also very constraining in this multifunctionalization process, for several reasons. The first is that the release of hydrogen which is a feature of the dehydrocondensation is an obvious menace which should be suppressed. The second arises from the fact that the reaction intermediate POS (II) containing Sixe2x80x94OR and containing Sixe2x80x94H (reactant =alcohol) is an oil which contains a large proportion of SiH, in the presence of platinum catalyst which is still active. This is a potentially dangerous mixture since the possibility of the reaction restarting and thus producing hydrogen in an unexpected and uncontrolled manner cannot be excluded, which represents, under such conditions, a high risk.
There is also an additional technical difficulty associated with the phenomena of intense foaming, induced by the hydrogen produced during the dehydrocondensation.
The examples of the process for the multi-functionalization of POSs containing SiH, as given in the closest prior art WO 96/16125, are batchwise laboratory tests, which do not take account of the industrial preoccupations outlined above.
Given this state of affairs, one of the essential aims of the present invention is to improve the process for the multifunctionalization of POSs described in WO 96/16125 in order to make it into an industrial process for the manufacture of multi-functional POSs which satisfies the requirements of viability and productivity, of quality of finished product, of safety and, lastly, of ease of implementation.
Another essential aim of the present invention is to provide an industrial unit for the manufacture of multifunctional POSs by dehydrocondensation/hydrosilylation, this device needing to be economical, reliable, of good performance and suited to the above-targeted manufacturing process.
These aims, among others, are achieved by the present invention, which relates, firstly, to a process for the continuous or semi-continuous manufacture of multifunctional polyorganosiloxanes (POS) (III) from POS (I) comprising SiH groups and according to a reaction mechanism involving a dehydrocondensation which allows the functionalization of the said POS (I) by the functionality (Fo1) and a hydrosilylation of at least one unsaturated compound which is a precursor of a functionality (Fo2) on the POS (III),
characterized in that it consists essentially in:
continuously supplying at least one continuous reactor A with:
at least one POS (I) containing SiH groups,
at least one functional reactant (HXR) containing labile hydrogen, preferably an alcohol and/or a thiol (X=O or S), the said
reactant preferably being in excess relative to (I),
and a catalyst comprising a product chosen from transition metalsxe2x80x94platinum being particularly preferred,
the said reactor A being the site of a dehydrocondensation leading, in particular:
to a POS (II) comprising residual SiH groups and SiFo1 groups (Fo1=XR),
to reactant HXR,
go and to a gas containing hydrogen and, optionally, gaseous reactant HXR,
allowing the continuous removal and recovery, from the reactor A, of the gas containing hydrogen as it is formed,
optionally collecting the liquid reaction medium provided that this medium contains, in particular, POS II containing SiH/SiFo1 groups and the catalyst,
transferring the said liquid reaction medium from reactor A to at least a reactor B for hydrosilylation of at least one unsaturated functional compound by the residual SiH groups of the POS (II), so as to obtain the POS (III) containing SiFo1 and SiFo2 groups,
allowing the above-targeted hydro- silylation to proceed,
recovering the POS (III) containing SiFo1/SiFo2 groups which is thus formed.
After long and laborious research, the Applicant has, to its credit, been able to demonstrate that the problem of industrialization of a multifunctionalization of POS involved performing a continuous dehydrocondensation, by providing for instantaneous and continuous removal and recovery of the hydrogen as it is formed and, moreover, by evacuating, as early and as quickly as possible, the dangerous POS (II) intermediate towards the other hydrosilylation reactor B in order to neutralize it and make it harmless. In other words, the hydrogen is removed and the reaction intermediate (II) is consumed as it is formed.
These advantageous process modes are guarantees:
of productivity/viabilityxe2x86x92continuous operation,
of qualityxe2x86x92control of the degree of conversion of the POS (I) into POS (II),
of safetyxe2x86x92maximum containment of the hydrogen risk,
and of ease of operation.
Incidentally, the process according to the invention conveniently allows the heat of reaction to be removed, while at the same time correctly controlling the temperature of the reaction bulk.
The bulk evacuation of hydrogen recommended provides a solution to the prohibitive problem of foaming.
Another advantage of the invention, and not the least of which, relates to the economy of this process.
The gas produced by the dehydrocondensation comprises reactant HRXxe2x80x94preferably an alcohol ROH, in vapour form. According to an advantageous mode of the invention, this gas is subjected to a treatment for separation of the hydrogen, preferably by condensation of the vapours of the reactant HRX (e.g. of alcohol).
In the present specification, R represents a hydrocarbon residue consisting of a linear or branched alkyl radical containing from 1 to 15 carbon atoms and preferably containing from 1 to 6 carbon atoms.
In the specific case in which the reactant containing labile hydrogen is an alcohol, the functionality Fo1 is an alkoxyl, and in the case where the unsaturated compound to be hydrosilylated is an olefin, Fo2 is a functional hydrocarbon radical corresponding to the same definition as that given for W in formula (II) of the unit constituting the functionalized PoSs, as described in WO 96/16125. This PCT application is, moreover, incorporated in its entirety into the present application by way of reference. The functionalities Fo1 are, for example, methoxy, ethoxy and (iso)propoxy. The functionalities Fo2 are, for example: an alkyl radical (i"") consisting of octyl, dodecyl, undecyl and tridecyl; an alkenyl radical (2i"") consisting of hexenyl and dodecenyl; an unsaturated cycloaliphatic radical (3i"") consisting of cyclohexenyl, l-methyl-l-cyclohexenyl, optionally linked to the silicon via a xe2x80x94CH2xe2x80x94CH2, xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94 or xe2x80x94(CH2) 3xe2x80x94 residue.
In order to provide further details regarding the process according to the invention, it may be indicated that reactor A is preferably supplied substantially simultaneously with POS (I) containing SiH and with functional reactant HXR, the catalyst being included in the POS (I) and/or the reactant HXR. Advantageously, the use of a solution of catalyst in the reactant HXR is favoured in practice.
Simultaneously supplying with POS (I) and with reactant containing labile hydrogenxe2x80x94such as an alcohol (ethanol)xe2x80x94in this way allows the safety to be improved since the bumping of the reaction and the release of hydrogen associated therewith can thus be controlled and tempered.
In order to optimize the kinetics of the dehydrocondensation reaction, preheating of at least one of the starting reactants, namely: POS (I), HXR and catalyst, to a temperature of between 30 and 100xc2x0 C., preferably between 40 and 80xc2x0 C., is ideally envisaged.
In accordance with the invention, one of the key points which makes it possible to ensure the reproducibility of the degree of conversion of the POS (I) into POS (II) and to ensure minimization of the potential risk associated with this unstable POS (II) involves:
carrying out the dehydrocondensation reaction in the continuous reactor A,
establishing a residence time which is just sufficient to obtain the desired degree of conversion,
and adjusting the reaction kinetics by controlling the operating parameters of the process (supply of reactants, temperature, etc.).
This residence time depends directly on the moment of transfer of the POS (II) into the reactor B. Thus, according to a preferred characteristic of the invention, the degree of substitution of the SiH groups with Fo1 is measured and/or calculated and the POS (II) is transferred from the dehydrocondensation reactor A to the hydrosilylation reactor B once the degree of substitution of the SiH groups with Fo1, expressed in mol%, is greater than or equal to 45, preferably to 55 and, even more preferably, is between 60 and 70. This is one of the means available, among others, for regulating the degree of substitution.
In the context of the actual control of the process according to the invention, the path from the degree of substitution to the degree of conversion may be followed, for example, by means of measuring the hydrogen released. The flow rate thus measured makes it possible, by calculation, to gain access directly to the degree of substitution. An alternative would be to set up continuous analysis of the POS (II).
In any case, instantaneous knowledge of the degree of substitution allows this degree to be adjusted by varying the operating parameters, in particular the residence time of the POS (I) and (II) in the reactor A and/or the reaction temperature and/or the supply rates of POS (I), of functional reactant HXR and of catalyst.
By providing for condensation of the vapours of volatiles, produced by the stripping effect brought about by the leaving hydrogen, it is possible to remove the heat of the reaction. This removal of heat takes place by means of vaporization of the volatile reactant fed continuously and by means of the condensation itself, given that, in addition, the recovered reactant condensate is recycled. The system is simple and self- regulating. Thus, the reaction temperature is regulated, for example, to about 70-71xc2x0 C. This regulation is another important factor for stabilizing the degree of conversion of the POSs (I) into POS (II), at the virtually asymptotic value of about 66%.
According to a preferred arrangement of the invention, the step of hydrosilylation of at least one unsaturated compound which is a precursor of Fo2 is carried out according to a continuous, semi-continuous or continuous mode, preferably continuously.
As regards the products used and the products obtained by this process, those disclosed in patent application PCT WO 96/16125 are preferred.
For further details, it will be pointed out that the multifunctional POSs (III) obtained by the process according to the invention are those comprising, per molecule:
xcex1) on the one hand, at least one functional siloxy unit (I):             (              R        xe2x80x2            )        a    ⁢                    Y        ⁢        Si            ⁡              (        O        )                            3        -        a            2      
where R"" is, in particular, a C1-C6 alkyl radical, Y is a C1-C5, preferably C1-C6, alkoxy radical, and a =0, 1 or 2;
on the other hand, at least one other functional siloxy unit (II):             (              R        xe2x80x2            )        b    ⁢            WSi      ⁡              (        O        )                            3        -        b            2      
where b =0, 1 or 2 and W is a C2-C30 hydrocarbon group, linked to the silicon via an Sixe2x80x94C bond, chosen from the following groups:
(i) a linear or branched alkyl group comprising at least 7 carbon atoms,
(2i) a linear or branched C2-C20 alkenyl group containing one or more double bonds in and/or at the end(s) of the chain(s), the said double bonds preferably being conjugated and/or combined with at least one activating group located in an xcex1 position and advantageously consisting of an oxide ether or a thioether,
(3i) an unsaturated aliphatic mono- or bicyclic group containing 5 to 20 cyclic carbon atoms and one or two ethylenic double bond(s) in the ring, optionally substituted with one or two linear or branched C1-C3 alkyl group(s), the said cyclic group optionally being linked to the silicon via a linear or branched C2-C10 alkylene radical,
(4i) a mercaptoalkyl group of formula
xe2x80x94R1xe2x80x94Sxe2x80x94A(4i)
in which
* R1 represents a linear or branched C2-C10alkylene radical optionally comprising at least one oxygen-containing hetero atom or an alkylene-cycloalkylene radical in which the alkylene part has the same definition as that given just above and the cyclic part contains 5 to 10 carbon atoms and is optionally substituted with one or two linear or branched C1-C3 alkyl group(s),
* A corresponds:
xe2x86x92 either to hydrogen,
xe2x86x92 or to a masking group M connected to S via a labile bond under given conditions and allowing the replacement of M with H or the creation of an active species xe2x80x94R1xe2x80x94Sxe2x80xa2;
(5i) a group comprising a polysulphuric species and corresponding to the following formula:
xe2x80x94R2xe2x80x94(xe2x80x94Sxe2x80x94)xxe2x80x94R3xe2x80x83xe2x80x83(5a) 
in which
* x =1 to 6,
* R2 having the definition as R1 above,
* R3 is a linear or branched C1-C10 alkyl,
(6i) a group containing at least one ring, in which at least one of the elements is a sulphur atom, and corresponding to the formulae below: 
in which
* i =0, 1 or 2 and j =1 to 6
* the substituents R4 and R5 are divalent radicals as defined above for R1,
(7i) a sulphoxide group of formula: 
in which the symbol R1 and M have the definitions given above for formula (4i); xcex3) and optionally at least one unit (III):             (              R        xe2x80x2            )        c    ⁢            (      H      )        d    ⁢            Si      ⁡              (        O        )                            4        -                  (                      c            +            d                    )                    2      
where c =0, 1, 2 or 3, d =0 or 1 and c +d xe2x89xa63.
To return to the implementation of the process according to the invention, it will be pointed out that, as regards the reagent containing a labile hydrogen, C1-C10, preferably C1-C6, alcohols are preferred. However, this does not exclude the use of their corresponding thiols.
As regards the unsaturated compound which is a precursor of Fo2, it is selected from compounds of appropriate structure capable of leading, by hydrosilylation, to the functionalities corresponding to groups (i) to (7i) defined above.
Preferably, the unsaturated precursor compounds are selected from olefins capable of leading to the functionalities Fo2 chosen from the groups (i), (2i) and (3i) defined above.
In practice, the catalyst is based on platinum. It may be, for example, platinum in oxidation state 0, such as the Karstedt catalyst, but also platinum in oxidation states II or IV. Another alternative is to use platinum catalysts supported on inorganic charges such as, e.g. carbon black, silica, alumina, etc.
It should be noted that, according to a variant of the process of the invention, a step of recovery of the gaseous mixture formed during the hydrosilylation may be envisaged. Such a gaseous-mixture is, in fact, formed of the vapours of the volatile reactant compounds of the dehydrocondensation (e.g. alcohol) or of the hydrosilylation (e.g. alkene). The said vapours are preferably condensed in order to recover them in liquid form and optionally recycle them in the process.
The present invention relates, secondly, to a device for carrying out, in particular, the process described above, the said device being characterized in that it comprises at least one continuous dehydrocondensation reactor A:
xe2x80xa2 connected to at least one pipe for supplying with starting reactants (POS (I) containing SiH groups/reactant containing labile hydrogen/catalyst), comprising:
means for the rapid evacuation and rapid recovery of the gas formed during the dehydrocondensation, p2 optional means for separating the hydrogen from other gases contained in the gas mixture formed,
optionally at least one vessel for receiving the POS (II) containing SiH/SiFo1 groups,
xe2x80xa2and connected by at least one pipe for transferring POS (II) containing SiH/SiFo1 groups in at least one hydrosilylation reactor B provided:
with means for recovering the vent gases, preferably combined with equipment for processing the vent gases in order to separate the hydrogen from the other gases,
and, preferably, means for stirring the hydrosilylation reaction medium.
Such a device is designed to meet the productivity/viability/quality/ease of implementation and safety criteria, already mentioned above, of the specifications sheet.
Its advantages and its embodiment variants will emerge from the description which follows, with reference to the single figure attached, of an exemplary embodiment of the said device. The illustration of the process will also be completed by reporting tests performed in accordance with the process and using the device of the invention.
The single figure attached is a schematic representation of an embodiment of a device for the continuous manufacture of multi-functional POSs by dehydrocondensation/hydrosilylation.